MUCC (Multiple UEs Cooperative Communication) refers to that: when an eNB (evolved NodeB) communicates with UE (user equipment), the UE may directly communicate with the eNB or may communicate with agent UE (also referred to as S-UE, that is, supporting user equipment) near the UE, and after the agent UE forwards data to the UE, communication is performed between the two UEs. In this way, UE with an optimal channel condition may be selected as the agent UE to transmit uplink and downlink data, so as to achieve an effect of multiuser diversity. Single link MUCC refers to that: agent UE acts as an agent for one or more UEs to communicate with an eNB, and the agent UE and the UEs form a UE group, where the agent UE and the eNB are connected in a synchronized state, the UEs and the eNB are connected in an out-of-synchronization state, and uplink data can be sent only by using the agent UE. When locations of the agent UE and the UEs for which the agent UE acts as an agent change, it may be necessary to hand over a serving eNB for the UE group.
Currently, when the agent UE and the UEs for which the agent UE acts as an agent need to perform handover, each piece of UE (including the agent UE and the UEs) that is in the UE group and that is allowed to perform handover needs to be handed over from an S-eNB (Serving eNB, serving eNB) to a T-eNB (target eNB), and each piece of UE that is allowed to perform handover needs to initiate a random access process, to separately perform handover.
During implementation of the present invention, the inventor finds that the prior art has at least the following problems:
In a process of handover of a UE group in the prior art, agent UE and each piece of UE to be handed over all need to initiate a random access process, to separately perform handover, which leads to a need of consuming a large quantity of Preambles and signaling; and for UEs in a single link MUCC state, as long as the UEs do not break off a cooperative relationship with the agent UE, the UEs still need to return to the out-of-synchronization state after being switched to the synchronized state, therefore it is unnecessary to perform an additional synchronization process for handover.